Alternate Experiment
by FinalMagus25
Summary: The sister AU to ExperimentTale, created by Gaster. In the year 203X, twenty years after the barrier is destroyed, a late teen gets caught in a series of events he doesn't understand, and as a result, obtains the curse called Determination. Now he must balance a broken life between fighting otherworldly evil and being a regular teen. What challenges will he face along the way?
1. Prologue

_**Prologue**_

Long ago, during the Medieval Ages, two races lived together in harmony: the humans and the monsters. Humans were creatures with strong enough body structure to not require magic to live. Thus, they could only learn to use magic through extensive training. Monsters had a more fragile body structure, so in order to live their lives like humans, most, if not all, were born with magic coursing through their veins. Monsters with magic could do many things that humans could not, which indirectly led to... their downfall.

You see, monsters had the uncanny ability to take human souls, and use their power to become stronger. And monster souls... were weak in comparison to that of humans, in spite of monsters being able to live as long as a millennium. They only had a fraction of the power of human souls, so when a monster died, they almost always turned into dust immediately rather than simply pass away. Human souls, on the contrary, persisted after the human died, allowing them to reincarnate into a new life.

Monsters in medieval times were mostly peaceful, and had no interest into stealing human souls to gain power. However, upon learning what monsters could do, the humans initiated a war with them out of fear. The war lasted only a few days, and strangely the humans appeared to be the victors. And so, the monsters were sealed underground by a magic spell in the base of Mount Ebott, creating a barrier that kept the monsters in, but it did nothing to keep humans from entering. It has been foretold that to free the monsters from their prison, the power of seven human souls must be used by a monster born with magic to break the magic barrier that trapped them there.

However, as the years passed, the secret of the monsters in the mountain became only a rumor, and only governments with top secret information on the subject truly knew of their existence. Conversely, monsters learned to make a living in the Underground, no longer carrying the desire to return to the surface. The monarchs of the Underground, Asgore and Toriel Dreemurr, ruled their kingdom in peace, while their son, Asriel, was soon to be the heir to the throne. Everything was perfect, until the year 189X, when... a human fell into the Underground.

Their name was Chara, and they were the first human to stumble into the mountain, hoping the fall would've killed them. Instead, upon entree, they met the kind, furry Asriel, who quickly brought them to his parents. After Chara was healed up, they were adopted by the Royal Family...

About a year later, after Asriel and Chara accidentally poisoned King Asgore via buttercups, they formulated a plan to free all the monsters from the Underground. Chara, due to learning the monsters' strife, wanted nothing more than to grant their freedom. But... the child also had ulterior motives. It was rumored that Chara had a deep, burning hatred for humanity...

Chara died a week later, the cause of death being buttercup consumption. As instructed, Asriel absorbed Chara's soul and crossed the barrier in an attempt to gather enough human souls to break the barrier. However, upon arriving at the human town of Ebott... he just couldn't bear to take a life. And so the frightened humans, fought back, mortally wounding Asriel Dreemurr. The prince arrived back at the Underground, and passed away in his father's own throne room, and turned to dust...

The deaths of both of his children sent King Asgore into a blind fury. Without thinking, his eyes filled with raging flames, he declared war on humanity, vowing to break the barrier and exact revenge. This lead to the eventual creation of the Royal Guard, an elite team of warriors trained to take the human souls. This also indirectly lead to the divorce of the King and Queen. Toriel, filled with disgust and heartache, went on a pilgrimage to the Ruins, where the old capital of the Underground stood in decay. And there she stayed, waiting for humans to fall into the Underground.

But until the time came...

She tended to the flowers.

**...**

201X

Then one day, hours before the monsters' freedom... she saw a figure in her flower field where humans fell. It was a skinny, white monster wearing a familiar attire, similar to the one she was wearing... But... it couldn't be...

"Asriel?"

**...**

**And so ends the prologue. I hope you enjoyed and are hoping to see more! See you later!**

**FinalMagus25**


	2. Episode Sans: Yet Darker

_**Episode Sans: Yet Darker**_

_My original timeline... lies somewhat inaccessible to me. The last I could glimpse was a girl, but not just any girl. Chara Dreemurr was in a defensive battle against a ghost-posessed dummy. She saw me before then, but I assume she didn't recognize me..._

_In any case... I'm back here... in The Void. I hate calling this home, but I'm afraid its the only one I have now. Here, time means nothing to me. I can appear whenever, and wherever I want in the timeline at will, if only for several seconds._

_But now I wish to move on. My... curiosity must be satisfied. I want to create a world that, rather than observe, I can manipulate. Yes... truly interesting._

_The Void has given me unique, yet terrifying power. If I'm not careful in making this new timeline, I'll be back at square one._

_Well... too late to turn back now..._

_Let's begin..._

**...**

_In the altered timeline, in 201X..._

Sans was asleep in his room, unaware that somebody was watching... He was dreaming of a bright future... He saw another skeleton, bearing a similar physique to him.

But something was off...

The other skeleton... his smile suddenly disappeared, and his eyes turned a bloody crimson. Sans slowly walked backwards in horror as pitch-black hatred oozed from the stranger's sockets. Sans turned to run out the door behind him, but there was no door! The other skeleton appeared right behind him, grabbed him right shoulder, and muttered one line.

"I'm not the only one you'll wrong..."

_**GAHHH!**_

Sans woke up hyperventilating before he could hear the rest, his left eye glowing from stress.

"Sans!" His wife screamed, bewildered. "A-Are you o-okay?"

Sans took a minute to calm down, still thinking about what the other him said.

"W-What h-h-happened?" She asked again with a worried look. "Bad dream?"

"Yeah... I'm fine. Just a nightmare." He replied.

"Whew... what a relief. Just don't wake the children, alright?"

"Yeah... sure. G'night, Alphys."

"Nighty night."

Alphys fell back asleep that night. But Sans didn't sleep again until the next night. The thought that he'll betray someone in the future... The thought terrified him.

**...**

**This chapter is important more to Alternate Experiment than to ExperimentTale, but I've uploaded this chapter onto both stories just in case. The Sans for Altered Experiment witnessed the dream in case you we wondering. This... is the true origin of Alternate Experiment. Also, yes, Gaster has the power of the Void, but he doesn't play a huge role in either story until later down the line.**

**FinalMagus25**


End file.
